THE ACTION OF U.V. LIGHT OF VARIOUS WAVELENGTHS ON PAPAIN

Abstract— Papain, prepared according to Kimmel and Smith is activated by irradiation with u.v. light of 254, 280 and 313 nm (φ_A= 0·022 ± 10 per cent). This activation is caused by the reductive splitting of a mixed disulfide in position 25. This disulfide is split with higher probability than any of the three structural disulfide links. This selectivity is likely caused by specific reduction of the mixed disulfide by thiol groups produced elsewhere in the molecule, although specific reduction by direct photochemical processes cannot be completely excluded on the basis of the data available. The quantum yields for destruction of structural cystine residues at the three wavelengths are comparable with the yields of cystine destruction in other proteins. The data also confirm that quanta absorbed by aromatic amino acid residues contribute to cystine destruction. In contrast to other enzymes with structural disulfide bonds, however, no correlation was found between the destruction of disulfide links and loss in activity. The results suggest that the mechanism of papain inactivation is not only dependent on the wavelength, but also on the dose.     

PHOTOCONTROL OF PHYTOCHROME DESTRUCTION IN GRASS SEEDLINGS. THE INFLUENCE OF WAVELENGTH AND IRRADIANCE

Abstract— –The kinetics of phytochrome destruction in vivo of coleoptiles and mesocotyls of etiolated grass seedlings (Avena sativa L., Zea mays L.) in continuous light were investigated using wavelength and irradiance as experimental variables. In contrast to dicotyledonous seedlings, the destruction reaction of these monocotyledons is saturated at very low levels of the far-red absorbing form of phytochrome, P_fr (e.g. at 1% of total phytochrome, corresponding to the photostationary state established by 727 nm light, in 2.5-day-old dark-grown Avena). On the other hand, the first-order rate constant of monocotyledon destruction may be at least one order of magnitude larger than in dicots, as indicated by the zero-order rate measured in the presence of saturating amounts of P_fr (τ_l/2 1.5 min in Avena). At sub-saturation P_fr levels, the destruction rate was found to be determined by the rate constants of the photoreactions over a wide range of wavelengths and irradiances. These results can be interpreted in terms of a destruction enzyme with high catalytic efficiency but limited availability. Analysis of in vivo binding of phytochrome to a pelletable cell structure during destruction revealed that both the pelletable and the non-pelletable fraction lose photoreversiblility with similar rates and thus provide no useful information with respect to a causal relationship between the two processes. However, due to the short half-life of P_fr at sub-saturation levels (which make the photoreactions and intermediary processes rate-limiting for destruction even at relatively high irradiances) the existence of a similarly rapid dark-reaction between the photoreactions producing P_fr and the destruction reaction could be demonstrated. This dark reaction displays the properties of P_fr binding to a receptor site.     

Radiolysis of water-nitrobenzene-carbon tetrachloride and water-chlorobenzene-carbon tetrachloride two-phase systems. Radiation yields of chloride ions

The influence of nitrobenzene and chlorobenzene on the total radiation yield of chloride ions in the -irradiation of water-carbon tetrachloride two-phase systems has been determined. Nitrobenzene at small concentrations shows a pronounced protective influence on the radiation destruction of carbon tetrachloride. Similar protective effect on the destruction of carbon tetrachloride is shown by chlorobenzene, too, but the decrease of radiation yields of chloride ions is smoother, which is explained by radiation decomposition of chlorobenzene itself. Protective effect of nitrobenzene and chlorobenzene on the radiation destruction of carbon tetrachloride is explained by transfer of energy from carbon tetrachloride molecules to the aromatic molecules.     

PHOTOCONTROL OF PHYTOCHROME DESTRUCTION AND BINDING IN DICOTYLEDONOUS vs MONOCOTYLE-DONOUS SEEDLINGS. THE INFLUENCE OF WAVELENGTH AND IRRADIANCE

Abstract— The irradiance and wavelength dependence of phytochrome destruction in vivo was analysed in etiolated cotyledons of Cucurbita pepo L. and etiolated seedlings of Amaranthus caudatus L. In contrast to grass seedlings, the rate of P _tot destruction could only be saturated by light sources that establish relatively high P _fr levels (about 50% of total phytochrome, corresponding to the photostationary state established by 693 nm light). To explain the irradiance dependence of P _tot destruction in dicots at irradiances above 0.1 Wm^-2, where the light reaction is at least one order of magnitude faster than P _fr destruction, we suggest there is a fast intercalary dark reaction between photoreaction and destruction. This dark reaction is probably—as in grass seedlings—the binding of P _fr to a receptor site. We conclude that the differences between dicots and grass seedlings with respect to the phytochrome system are of a quantitative rather than a qualitative nature.     

Electrochemical treatment (EChT) effects in rat mammary and liver tissue. In vivo optimizing of a dose-planning model for EChT of tumours.

BACKGROUND: A reinvented technique for tumour therapy, electrochemical treatment (EChT), is attracting increasing attention. This study compared results from treatment of liver and mammary tissue focusing on destruction and pH changes in the tissue close to the treatment electrodes. Subsequently, data were compared with a dose-planning model. METHODS: Mammary or liver tissue in 50 adult female Sprague Dawley rats was given EChT with a constant, direct current. The electrodes used were Pt/Ir (9:1) with spherical tips. In situ pH measurements were taken with a micro-combination glass electrode. RESULTS: Spherical lesions were produced in both liver and mammary tissue. No significant difference was detected when comparing the size of the lesions in the two kinds of tissue. Similar pH profiles were obtained in tissue surrounding the electrodes, with pH values changing rapidly from unphysiological to neutral status within the space of a few millimetres. The pH at the border of the macroscopic destruction zone, regardless of tissue type or coulomb dosage, correlated well with specific values (4.5-5.5 at the anode and between 9 and 10 at the cathode). CONCLUSION: The analogous destruction patterns in mammary and liver tissue support the hypothesis that EChT has similar results in at least these two different types of tissue. This implies that the destructive pattern caused by the treatment may be the same also in tumours.     

Formation and dissolution processes of the 6-thioguanine (6TG) self-assembled monolayer. A kinetic study

This is a report on the kinetics of the destruction and formation processes of the 6-thioguanine self-assembled monolayer (6TG SAM) on a mercury electrode from acid solutions by chronoamperometry. The destruction of the 6TG SAM that has been previously formed under open circuit potential conditions is carried out by stepping the potential from an initial value where the chemisorbed layer is stable up to potentials where the molecules are no longer chemisorbed. The destruction of the SAM has been described by a model that involves three types of contributions: (i) a Langmuir-type adsorption process, (ii) a 2D nucleation mechanism followed by a growth controlled by surface diffusion, and (iii) a 2D nucleation mechanism followed by a growth at a constant rate. The nonlinear fit of the experimental transients by using this procedure allows the quantitative determination of the individual contributions to the overall process. The kinetics of the formation process is studied under electrochemical conditions. The chronoamperometric experiment allows us to monitor the early stages of 6TG SAM formation. The implications of the physisorbed state at low potentials in the type of monolayer formation and destruction processes as well as the influence of temperature are also discussed.     

Hormonal and dim light effects in retinal photodamage.

Abstract—Exposure of albino rats to continuous visible dim light results in the rapid. but graded. loss of photoreceptor cells. The age at which albino rats are exposed to light influences the degree of photoreceptor damage. The severity of cell destruction per unit exposure time gradually increases in rats exposed at different ages from postweaning to adulthood, and by 8 weeks of age, reduction in the thickness of the outer nuclear layer (photoreceptor cell nuclei) is highly significant. The period of increasing susceptibility to light damage is coincident with the occurrence of sexual maturation, which suggests a relationship between photoreceptor destruction and the maturation of the pituitary gland-gonadal axis. To determine whether the absence of the pituitary gland and ovarian hormones influences photoreceptor damage, animals were either hypophysectomized or ovariectomized and exposed to continuous illumination for up to 45 days. The degree of photoreceptor destruction is significantly reduced in operated, as compared with sham-operated control, rats exposed to an identical light regimen. Small, physiologic doses of estradiol reverse the protective effects of ovariectomy, but larger, pharmacologic doses do not. Retinal damage is significantly enhanced by injection of pituitary homogenates during the light-exposure period and by transplantation of pituitary glands under the kidney capsule of rats in which the pituitary has been removed. Pituitary glands transplanted in this location produce high levels of prolactin, while other pituitary hormones are found at unusually low, and sometimes nonfunctional, levels. Prolactin administration to rats during the light exposure period effectively reverses the protection afforded by removal of the pituitary gland. Pituitary gland hormones as well as hormones from some of the pituitary target organs, appear to have a regulatory influence on the severity of light-induced photoreceptor damage in this species.     

A study on modified polymers by means of i.r. spectroscopy and thermal analysis

Curing and destruction of phenol-formaldehyde resins, modified with waste oligomer resin from phenol production, were studied by means of i.r. and ESR spectroscopy and thermal analysis. In the process of curing synthesized polymers with hexamethylene tetramine, the latter was found to decompose giving dimethyleneimine and other products causing cross-linking of the polymers. Incorporation of nitrogen in the polymer was proved by means of i.r. spectra and elemental analysis. The activation energy of decomposition was determined by thermogravimetry. Analysis of ESR spectra suggested that free radical processes participate in curing and decomposition of phenol-formaldehyde polymers modified with waste phenol resin.     

Polymeric nature of selenium crystallization. II. Crystallization kinetics and secondary crystallization

The crystallization of elemental selenium has been studied in light of present concepts of crystallization in organic polymers. Bulk-crystallization kinetic data as measured by a dynamic density technique and spherulite growth-rate data as measured by optical microscopy are presented for the temperature range 70°C to 160°C. Plots of extent of isothermal crystallization versus time were sigmoidal in shape. Spherulite growth rates were constant for a given temperature and reached a maximum at approximately 130°C. Evidence is presented for secondary crystallization in selenium, and a model is proposed for destruction of chain folds with interlamellar crystallization during the spherulitic-to-“metallic” transformation above 100°C.     

THEORETICAL ASPECTS OF THE U.V. INACTIVATION OF PROTEINS CONTAINING DISULFIDE BONDS

Equations are proposed for the estimation of quantum yields for cystine destruction and disulfide protein inactivation during u.v.-irradiation in acidic and neutral solutions. The formulas permit a discussion of energy transfer from excited aromatic amino acids to cystines and/or of chemical reactions between excited tryptophans or tyrosines and cystines. The results are discussed with regard to general aspects of the photo-biochemistry of enzymes.     

Studies on internal structure of tablets. III. Manufacturing of tablets containing microcapsules

The aim of this study was to establish the best manufacturing conditions for preparation by the direct compression method of tablets which contain microcapsules having a minimal destruction rate of the coating wall, show the same dissolution pattern as microcapsules, and have enough mechanical strength for practical use, and to elucidate the internal structure of the tablets under the best manufacturing conditions. Degree of destruction of the microcapsule wall was evaluated by the dissolution rate of the medicine in the microcapsules. To learn the mechanical strength of tablets, the crushing strength and friability were measured; their internal structure was analyzed by the porosity and pore size distribution. The best manufacturing conditions for the tablets were thus determined, and it was clarified by analysis of the internal structure that these conditions are markedly affected by the flowability of prescribed powders and the packing state at compression.     

THEORETICAL ASPECTS OF THE U.V. INACTIVATION OF PROTEINS CONTAINING DISULFIDE BONDS

Abstract Equations are proposed for the estimation of quantum yields for cystine destruction and disulfide protein inactivation during u.v.-irradiation in acidic and neutral solutions. The formulas permit a discussion of energy transfer from excited aromatic amino acids to cystines and/or of chemical reactions between excited tryptophans or tyrosines and cystines. The results are discussed with regard to general aspects of the photo-biochemistry of enzymes.     

Heterogeneous-catalytic decomposition of ethylenediaminetetraacetic acid and its complexes with iron,nickel, and cobalt on carbon materials in nitrate media

Catalytic thermal destruction of ethylenediaminetetraacetic acid and its complexes with nickel, iron, and cobalt in nitrate solutions on carbon materials (activated unwoven material, sibunite, and BAU–A activated carbon) was studied. The activation energies of thermal destruction were calculated.     

Chemometric approaches in environmental problems concerning PCDD and PCDF. Data interpretation and source correlation. Mechanisms of formation and destruction in MSW combustion process

Summary The role of multivariate analysis methods in evaluating, rationalizing, and working out complex environmental problems is discussed. The discussion is organized in two sections; a literature analysis of the application of chemometric methods to PCDD/PCDF data interpretation and source correlation and a review of the role of chemometric methods in analysing the results obtained by the Authors studying PCDD/PCDF formation and destruction mechanisms in MSW combustion processes.     

Abatement of Trichloromethane by Using Nonthermal Plasma Reactors

This work investigated the destruction of a halogenated carbon (trichloromethane) using different types of nonthermal plasma reactors. Three reactors, i.e., a surface discharge reactor, a dielectric-packed bed reactor and a barrier discharge reactor with a perforated dielectric tube, were compared with respected to the trichloromethane destruction efficiency. The effect of oxygen content and input power on the trichloromethane destruction was examined, and the byproducts were analyzed to elucidate the destruction pathways. The dielectric-packed bed reactor was found to show better performance in the trichloromethane destruction than the other two reactors. The increase in the oxygen content decreased the destruction efficiency, and the highest destruction efficiency was obtained at oxygen content 0.5%. The calculations for electron-molecule collisions indicated that the most abundant reactive species initiating the destruction of trichloromethane are metastable nitrogen molecules. The major byproducts were CO and Cl₂, and the formations of NO₂ and N₂O were also significant.     

Destruction of polymers and adhesion layers

A review of the main ideas of the modern concept of polymer destruction. A separate chapter is devoted to the adhesion destruction of glued joints.     

The specific features of the liquid-phase oxidation of saturated esters. Kinetics,reactivity and mechanisms of formation of destruction products

Russian Chemical Bulletin - Data on kinetics, reactivity, and mechanisms of formation of destruction products of the liquid-phase oxidation of saturated esters by molecular oxygen have been...     

Determination of picomole amounts of formaldehyde in air and bio-fluids based on its enhanced myoglobin-luminol chemiluminescence reaction

Abstract

The aim of this study was to assess the performance of selected destruction methods for the determination of heavy metals (Cd, Cu, Pb and Zn) in woodlouse (Oniscus asellus). A vigorous total analysis involving microwave destruction with HF, HCl and HNO₃ (method 1) was used as a reference method. Consistently low values for the dry ashing method may indicate incomplete dissolution of the elements and/or losses through volatilisation. Method 3 (concentrated HNO₃) that frequently is used in literature, produced erroneous values for Cd, Cu and Pb. Results were consistent with the microwave digestion, provided H₂O₂ was used during digestion (method 4, HNO₃/H₂O₂). Method 5 (HNO₃/HCIO₄, one destruction step) yielded low recoveries when only one destruction step was applied. Applying two destruction steps (method 6) resulted in values consistent with the microwave method, but was at the expense of reproducibility and rendered the method more lengthy and laborious. Because of the very good performance combined with speed and simplicity, destruction with HNO₃/H₂O₂ (method 4) emerged as the most convenient method.     

Partialsynthetische Aristolochiasäuren und Analoge. 3. Mitt.: 3,4,6-Trimethoxy-7-ethoxy- und 3,7-Diethoxy-4,6-dimethoxy-10-nitrophenanthren-1-carbonsäuren

Two further aporphine alcaloids, N-methyllaurotetanine and boldine, were used to the synthesis of aristolochic acid analogs. By means of their destruction and nitration of the reaction products two new nitrophenanthrene acids were obtained and their chemical structures were proved.

     

Mesoporous materials with an acidic framework and basic pores. A successful cohabitation

Bifunctional mesoporous material with an acidic framework and basic pores was synthesized via the co-condensation of TEOS, bistrimethoxysilylated precursors with a disulfide core, and 3-tert-butyloxycarbonyl (aminopropyl)triethoxysilane using P123 as surfactant; the reduction of disulfide units to SH groups followed by their oxidation into SO3H and deprotection of amino groups gave rise to a material containing two antagonist functionalities located at the nanometric scale in a successful cohabitation, avoiding their mutual destruction in the presence of aprotic solvent. This kind of material illustrates the large possibilities offered by mesoporous materials and opens new and unsuspected applications.